Testing x64 components on DF2021 and I came across this warning/issue:

----Compiler Warning Summary----
Warning 4543: cComChilkatSFtpFile.pkg (ln 250) Redefining function return type for GET_COMOWNER with STRING (first defined as INTEGER)
Problem here is that function ComOwner has been defined in cCJCommandBars.pkg with a different return type.

IMHO, If the class is of type MIXIN then the complier should skip/ignore these warnings.